[jcr]

The two most common methods are "Screen Readers" (audio) [1] and "Braille Displays" (touch) [2]. Depending on the exact vision impairment, other alternatives also exist (magnifiers, customized color/brightness, and so forth).

[1] http://en.wikipedia.org/wiki/Screen_reader

[2] http://en.wikipedia.org/wiki/Refreshable_braille_display

Good Luck with your situation!